1. Technical Field
The disclosed subject matter relates generally to metal insulator field effect transistors and methods of making the same, and more specifically to vertical field effect transistors and metal insulator field effect transistors comprising of group-III nitride materials and/or zinc insulator based semiconductor field effect transistors.
2. Description of the Related Art
A vertical field effect transistor (VFET) is a unique class of a three terminal transistor. A VFET includes source, drain and gate electrode terminals, and the VFET sustains electric fields between the source and drain terminals vertically. A VFET is typically manufactured using silicon-based semiconductor materials. The advantage of using silicon-based materials includes a cost-efficiency and a high performance. The high performance of silicon-based VFET is attributed to a low defect interface between the silicon and a gate dielectric. The gate dielectric is a material suspended between the semiconductor layers and the gate electrode and is employed to achieve a field effect in a transistor. The insulator can include a silicon dioxide insulator and/or other “high-K” dielectric insulators, such as a hafnium insulator.
However, silicon-based VFETs have fundamental limitations. First, silicon-based VFETs cannot operate at high voltages because of the silicon's properties. The critical field of a material can be considered a strength of an electric field beyond which a material breaks down and losses its semiconductor properties. Because silicon has a relatively low energy band gap (e.g., 1.14 eV), the critical field of silicon is low. Therefore, silicon-based VFETs are not amenable to operating at high voltages. Second, the switching frequency of silicon-based VFETs is oftentimes below 100 kHz. Third, the on-resistance of silicon-based VFETs is often high, e.g., above 200 mΩ-cm−2. Lastly, the operating temperature of silicon-based VFETs can be low, e.g., around 150° C.
Some of the deficiencies of silicon-based VFETs can be addressed by silicon carbide (SiC) based VFETs. The higher band gap of SiC (e.g., 3.0 eV) enables a higher operating voltage of VFETs, up to 10,000V, higher switching frequencies, desirable lower on-resistances, and higher operating temperatures of about 230° C.
However, SiC-based VFETs are expensive to manufacture. To manufacture a power transistor that can accommodate up to 10,000V, the SiC epitaxial layer in the transistor should be substantially thick, e.g., in the range of 10 μm-100 μm. Because such a thick SiC epitaxial layer is required, the levelized cost to manufacture a SiC-based VFET can be up to 100 times more expensive compared to a silicon-based VFET. Furthermore, the on-resistance of a SiC epitaxial layer can be high, which can limit the performance of the SiC-based VFET. The high cost of manufacturing, as well as limited performance, slowed the adoption of SiC in power transistors.